1. Field of the Invention
This invention relates to a mechanism for providing a relatively high, and relatively stable, DC voltage from a relatively low and unstable DC voltage source.
2. Prior Art
Dahlinger et al, in U.S. Pat. No. 3,569,818, issued Mar. 9, 1971, discloses a DC voltage regulator utilizing a transistor switch in the primary circuit of a transformer and providing a regulated output voltage at a rectified output of the transformer secondary coil. A comparator turns on the transistor switch whenever the regulated output voltage falls below a predetermined level. Feedback circuitry to the comparator differs substantially from that of the subject converter and the switching rate is not controlled as a function of unregulated source voltage.
Sautel, in U.S. Pat. No. 3,611,105, issued Oct. 5, 1971, discloses a DC voltage converter for converting a DC source voltage into a regulated voltage at a floating potential with respect to ground. Current from the source is switched by a transistor in series with the source and a primary transformer winding to provide a chopped output current at the secondary winding which is rectified and filtered to provide the regulated output voltage. A feedback loop from the regulated output to a comparator effects a time modulated control of the switching transistor to maintain the output at a predetermined voltage level under load variation. Although operation of this converter generally resembles that of the subject converter, the transistor is switched at a fixed frequency at varying duty cycles while the switching transistor of the subject converter is switched at both varying frequencies and duty cycle. Also, the feedback circuitry is dissimilar from that of the subject converter.
Brokaw, in U.S. Pat. No. 3,790,878, issued Feb. 5, 1974, discloses a switching regulator for providing a regulated DC output voltage. Energy from an unregulated DC voltage is periodically dumped into a transformer primary winding under the control of a switch in series with the source voltage and the primary winding. The energy is transferred to the transformer secondary winding and then rectified, filtered and applied to the load. The ratio of switch-on time to switch-off time is dependent upon several factors including a feedback voltage proportionate to the output voltage. The Brokaw regulator operates in a manner resembling that of the subject converter and includes similar feedback circuitry to a comparator, but circuitry for controlling a comparator input as a function of source voltage is not disclosed.